Can mountain-climbing bears rescue cherry trees from global warming?

http://www.eurekalert.org/pub_releases/2016-04/cp-cmb041816.php

ublic Release: 25-Apr-2016
Can mountain-climbing bears rescue cherry trees from global warming?
Cell Press

As the planet warms, one way for plants and animals to find their way to cooler territory is to move up higher into the mountains. Now, researchers reporting in the Cell Press journal Current Biology on April 25 have found that cherry trees are indeed making their way to the mountaintops with help from an unexpected source: mountain-climbing bears.

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"Most previous studies have predicted future plant distributions under global warming based on the simple relationships between present plant distribution and environmental factors there, assuming that there are no seed dispersal limitations and no bias in dispersal direction. However, our study indicates that predicting future plant distributions can be very uncertain without considering the seed dispersal process that determines plant movement."

In the case of cherry trees, it's all about the bears.

If the goal is to seek cooler temperatures, then moving to higher altitudes is a rather useful strategy, the researchers explain. That's because the temperature change with increasing altitude is about 100 to 1,000 times greater than can be obtained by moving the same distance to the north or south.

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"We show that bears disperse seeds toward mountaintops, probably because bears climb mountains following the spring plant phenology, proceeding from the foot to the top of mountains," Naoe says.

The dispersal distance of the seeds was considered to be sufficient for the cherries to cope with global warming. The distance that the bears and martens moved the seeds corresponded to a drop in temperature of about 1.0°C or 2.0°C, enough to offset the projected global temperature rise of almost 5°C by the year 2100.

While the findings come as good news for cherry trees, they are a reminder that the movement patterns of individual plants in nature will be hard to accurately predict without careful consideration of their complex interactions with seed-dispersing animals, the researchers say. Estimates suggest that more than one-third of plants depend on animals to disperse their seeds.

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